The present invention relates to electromagnetic transducers for information storage and retrieval systems, such as disk or tape drives.
FIG. 1 is a schematic top view of a disk drive storage system 20, including a spinning disk 22 coated with a media layer 23 and a transducer 25 held by an arm 28 for storing and retrieving information on the media. Such a drive system 20 may have another transducer for storing and retrieving information on another media layer on an opposite side of the disk 22, and may have additional disks and associated transducers, not shown. The transducer 25 may be attached to a slider that is held near a free end of the arm 28 by a gimbal structure. The transducer 25 writes and reads data on multiple concentric tracks of the disk 22 such as track 30. To instead write and read data on another track 31 that is near a center 33 of the disk 22, the arm is driven by an actuator, not shown, to move the transducer toward the center 33. By sweeping the arm 28 over the surface of the disk 22, as shown by arrow 35, the transducer 25 can access the multiple data tracks. The orientation of the transducer, however, is skewed relative to tracks such as 30 and 31 disposed near outer and inner radiuses of the media layer.
Current commercially available disk drives store data in domains having magnetizations that are substantially parallel to tracks such as tracks 30 and 31, which is sometimes called longitudinal recording. It has been predicted that such longitudinal magnetic storage will become unstable at normal operating conditions when the domains reach a minimal size, termed the superparamagnetic limit. In order to store the data at higher density, the drive system 20 may instead be designed to store data in domains that are substantially perpendicular to the disk 22 surface, which may be termed perpendicular recording.
FIG. 2 is a schematic side view of a prior art system for perpendicular recording, including a transducer 50 positioned in close proximity to a surface 55 of a disk 52 that is moving relative to the transducer in the direction of arrow 58. The disk has a media layer 60 that has an easy axis of magnetization that is substantially perpendicular to the disk 22 surface. The disk also has a low-coercivity, high-permeability (xe2x80x9csoft magneticxe2x80x9d) underlayer 62 that provides a path for magnetic flux, allowing the flux 64 written by the transducer to be directed substantially perpendicular to the disk surface. The transducer 50 includes a write pole 66 and a return pole 68 that are magnetically coupled by a magnetic layer 70 in the transducer and by the underlayer 60 to form a magnetic circuit, with the write pole 66 communicating a more concentrated flux 64 through the media 62 than the return pole 68, for magnetizing the media adjacent the write pole.
FIG. 3 illustrates a prior art pattern of magnetization 70 of such a write pole 66 for a track such as track 30 where the transducer is skewed relative to the track. The write pole has a conventional rectangular area facing the media, which is reflected in the most recent magnetization 72. Prior magnetizations written to the media, such as magnetization 71, have edge effects or side writing 75 from the skew that may lead to errors in reading data.
In accordance with the present invention, write poles having a leading edge that is smaller than a trailing edge are disclosed, which can reduce erroneous writing for perpendicular recording systems. The write poles may have a trapezoidal shape when viewed from a direction of an associated media. The write poles may be incorporated in heads that also contain read elements such as magnetoresistive sensors, and may be employed with information storage systems such as disk drives.